Hino-Maeshima Laboratory

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Research

1．Interaction between light and semiconductor quantum nanostructures

Floquet states are electronic systems driven by strong CW THz laser form photodressed electron states. We develop new quantum many-body methods dealing with these photodressed particles as fundamental quasi-particles, and explore new pnotoinduced phenomena. In particular, we study dynamic correlation and non-equilibrium quantum dynamics induced by correlation effect and interband photo-excitation of composite particle system (exciton, charged exciton, exciton molecule, etc.).
[K.Hino, X. M. Tong and N. Toshima,“Interacting dynamic Wannier-Stark ladder driven by a periodic pulse train”, Phys. Rev. B 77, 045322_1-19 (2008)]

Quasienergies of electron-hole joint band of laser-driven semiconductor superlattice(a)with exciton effect(b)without exciton effect. (a)Time-Delay spectrum and (b)Pondermotive potential energy at Ponderomotive radius 50 (a.u.) of dynamic Wannier-Stark ladder electron.

2．Photoinduced phase transition in strongly correlated electron system

We study photoinduced phenomena in strongly correlated electron systems listed below.

(1) We have studied photo-induced phenomena in the organic spin-Peierls material K-TCNQ and revealed that (i) the polaron state is caused by intermolecular lattice distortion produces mid-gap absorption, (ii) intramolecular distortion also causes a polaron state but produces absorption peaks different from those experimentally observed.
[N.Maeshima and K.Yonemitsu, “Polaronic States with Spin-Charge-Coupled Excitation in a One-Dimensional Dimerized Mott Insulator K-TCNQ”,J.Phys.Soc. Jpn.77,074713_1-6(2008)]
(2) We have shown that the Drude-like low-energy component develops in the optical conductivity of the photoexcited state of the one-dimensional two-orbital Hubbard model. In addition, we have clarifiyed that the photoexcited carriers also induce characteristic spectral peaks reflecting spin multiplets, which are different from those in the single-band systems.